MR imaging has been used extensively in clinical practice for tumor diagnosis. A wide variety of functional MRI techniques have also been developed to non-invasively assess tumor flow and oxygenation. In particular dynamic contrast enhancement (DCE) MRI has been shown to correlate well with tumor angiogenesis. BOLD effects have also been used to measure changes due to blood oxygenation and flow in tumor studies. With careful experimental design, BOLD effects may also provide quantitative information about oxygen saturation. Recently we have been developing a novel MR imaging technique based on intermolecular double-quantum coherences (iDQCs), which is inherently more sensitive to some physical processes relevant to tumor physiological characterization. In this application, we propose three different types of MRI measurements based on iDQCs, which will provide more sensitive and specific characterization of tumors in terms of: (1) oxygenation; (2) spatial distributions of microvessels at spatial resolutions far below conventional MRI; and (3) necrotic fraction. In the this phase, iDQC imaging methods suitable for tumor characterization will be developed and compared with conventional SQC MRI. Experimental murine tumor models, MCA-35 and MCA-4, which have been extensively characterized by the co-PI, Dr. Fenton, with immunohistochemical techniques, will be used for iDQC MR imaging on a 9.4T MR scanner. Histograms of physiological parameters measured with iDQC imaging will be compared to results from immunohistochemical measurements and conventional SQC MR/. Correlation will be sought in selected regions in the tumor core and periphery, as well as normal tissues. In the next phase, methods for multispectral analysis of images will be developed to address the multi-dimensional nature of tumor pathophysiology with integrated data from oxygen saturation, microvascular distribution, and tumor necrotic fraction measurements. Spatial correlation between MRI and immunohistochemical images for quantifying blood vessel distribution and oxygen saturation will also be pursued in this phase. Response to increased oxygen and effects of radiation therapy on tumor oxygenation and angiogenesis will be studied to validate the utility of new iDQC imaging techniques. The novel iDQC MR imaging proposed in this study will provide enhanced sensitivity and specificity for measurements based on the BOLD effect, and provide a new measurement for tumor vascularity complementary to conventional DCE techniques. Since the iDQC techniques proposed in this application do not involve changes in hardware, they can be translated into clinical applications relatively quickly once the methods are carefully validated.